User blog comment:Flia/Canon material/@comment-1512913-20111211013944

Add to that only Arkham and Vergil knew the location of the seal and the clown was there. Also Vergil was not concerned about the clown's presence. At one point the look in his eyes changes and he starts to speak like Arkham. Well ability to change form, flying, illusions and other weird things looks too much for a human even though Arius could do some things.
 * 50/50 canon or not
 * Yes, this is the shadow I was talking about.

In manga it was just because and he was crazy.
 * in game he sure had some reason to gain power, also his to protect line.

So if book says something, and game something else ... the game version prevails. The issue with this manga is that there are as many reason to consider it canon as many reason to not. Im not an admin, its up to you.
 * Post by Capcom stuff stated that things from books are to be considered canon until contradicted.